PT-2026-42132 · Nlnet+4 · Unbound+4

Qifan Zhang · Published 2026-05-20 · Updated 2026-06-30 · CVE-2026-42959

Positive Technologies (AI Summary)

CVSS v3.1

7.5

High

Base vector

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Name of the Vulnerable Software and Affected Versions NLnet Labs Unbound versions prior to 1.25.1

Description A denial of service issue exists in the DNSSEC validator. When constructing chase-reply messages for validation, the software uses an incorrect counter to calculate write offsets for ADDITIONAL section rrsets. DNAME duplication can increase the ANSWER section count, while authority filtering can decrease the AUTHORITY section count, creating an uninitialized array slot. The validator subsequently dereferences this uninitialized pointer, leading to a process crash. An attacker controlling a DNSSEC-signed domain can trigger this by configuring a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records along with signed ADDITIONAL glue records.

Recommendations Update to version 1.25.1.

Fix

DoS

Access of Uninitialized Pointer

Weakness Enumeration

CWE-824

Related Identifiers

ALSA-2026:23231

ALSA-2026:24365

ALSA-2026:24369

CVE-2026-42959

ECHO-2FCE-8B09-C05E

OPENSUSE-SU-2026:10903-1

OPENSUSE-SU-2026:21083-1

RHSA-2026:23231

RHSA-2026:24365

RHSA-2026:24369

SUSE-SU-2026:22160-1

SUSE-SU-2026:22213-1

SUSE-SU-2026:2369-1

USN-8282-1

USN-8282-2

Affected Products

Freebsd

Linuxmint

Rocky Linux

Ubuntu

Unbound

References · 84

• https://errata.rockylinux.org/RLSA-2026:24365 · Vendor Advisory
• https://access.redhat.com/errata/RHSA-2026:24365 · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2026-42959 · Vendor Advisory
• https://errata.almalinux.org/9/ALSA-2026-24369.html · Vendor Advisory
• https://osv.dev/vulnerability/ALSA-2026:23231 · Vendor Advisory
• https://access.redhat.com/errata/RHSA-2026:24369 · Vendor Advisory
• https://osv.dev/vulnerability/SUSE-SU-2026:22160-1 · Vendor Advisory
• https://osv.dev/vulnerability/openSUSE-SU-2026:21083-1 · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-42959 · Vendor Advisory
• https://osv.dev/vulnerability/SUSE-SU-2026:2369-1 · Vendor Advisory
• https://osv.dev/vulnerability/USN-8282-1 · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2026-42959 · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-44608 · Vendor Advisory
• https://errata.almalinux.org/10/ALSA-2026-23231.html · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-42944 · Vendor Advisory